Fix compilation of rtc_base_objc on iOS when building as part of Chromium.

webrtc/base/BUILD.gn

Index: webrtc/base/BUILD.gn
diff --git a/webrtc/base/BUILD.gn b/webrtc/base/BUILD.gn
index 0f7450cfa6d7c4266ea578bb03b180750bbd5625..e7418d20a007de620548e6fe8ae122f36b812e85 100644
--- a/webrtc/base/BUILD.gn
+++ b/webrtc/base/BUILD.gn
@@ -619,8 +619,6 @@ if (is_ios) {
       "objc/RTCDispatcher.m",
       "objc/RTCFieldTrials.h",
       "objc/RTCFieldTrials.mm",
-      "objc/RTCFileLogger.h",
-      "objc/RTCFileLogger.mm",
       "objc/RTCLogging.h",
       "objc/RTCLogging.mm",
       "objc/RTCMacros.h",
@@ -631,6 +629,13 @@ if (is_ios) {
       "objc/RTCUIApplication.h",
       "objc/RTCUIApplication.mm",
     ]
+
+    if (!build_with_chromium) {
+      sources += [
+        "objc/RTCFileLogger.h",
+        "objc/RTCFileLogger.mm",
+      ]
+    }
   }
 }